Efficient Multiplex Genome Editing Tools Identified by Protoplast Technology in Phalaenopsis

Phalaenopsis orchids are popular ornamental plants worldwide. The application of the efficient multiplex genome editing tools in Phalaenopsis, will greatly accelerate the development of orchid gene function and breeding research. In this study, we establish a fast and convenient Phalaenopsis protoplast platform for the identification of functional genome editing tools. Two multiplex genome editing tools, PTG-Cas9 (PTG, polycistronic tRNA gRNA) system and PTGm-Cas9 (PTG-Cas9 system with modified sgRNA structure) system are designed to edit PDS gene of commercial Phalaenopsis ST166 at four target sites. We find that both PTG-Cas9 and PTGm-Cas9 system are functional in Phalaenopsis, and the PTGm-Cas9 system with modified sgRNA has a higher editing efficiency than PTG-Cas9 system. Further, we design another multiplex genome editing tool, termed as DPII-Cpf1 system (dual Pol II promoter to drive the expression of Cpf1 endonuclease and crRNA), to edit PDS gene of Phalaenopsis at four target sites likewise. All the four targets are efficiently edited by DPII-Cpf1 system, and the total mutation rate is about 3 times higher than that of PTGm-Cas9 system. Taken together, using the Phalaenopsis protoplast platform, we successfully establish two efficient multiplex genome editing tools for Phalaenopsis research, PTGm-Cas9 and DPII-Cpf1. The multiplex genome editing tools established in this study have great application potentials in efficiently constructing large-scale knockout mutant libraries of orchid and speeding up orchid precise breeding.